AU2021252630A1 - Infrared reflectivity control device - Google Patents

Infrared reflectivity control device Download PDF

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Publication number
AU2021252630A1
AU2021252630A1 AU2021252630A AU2021252630A AU2021252630A1 AU 2021252630 A1 AU2021252630 A1 AU 2021252630A1 AU 2021252630 A AU2021252630 A AU 2021252630A AU 2021252630 A AU2021252630 A AU 2021252630A AU 2021252630 A1 AU2021252630 A1 AU 2021252630A1
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AU
Australia
Prior art keywords
control device
infrared
surface area
electrodes
infrared reflectivity
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AU2021252630A
Inventor
Pierre Henri AUBERT
Jonathan CHRUN
Laurent Dupont
Sébastien FAGOUR
Stephen LEGALL
Eric Petitpas
Cedric Vancaeyzeele
Frédéric VIDAL
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Nexter Systems SA
Institut Mines Telecom IMT
CY Cergy Paris Universite
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Cy Cergy Paris Univ
Nexter Systems SA
Institut Mines Telecom IMT
CY Cergy Paris Universite
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Publication of AU2021252630A1 publication Critical patent/AU2021252630A1/en
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    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/165Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
    • G02F1/166Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect
    • G02F1/167Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect by electrophoresis
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1343Electrodes
    • G02F1/134309Electrodes characterised by their geometrical arrangement
    • G02F1/134363Electrodes characterised by their geometrical arrangement for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/165Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
    • G02F1/1675Constructional details
    • G02F1/1676Electrodes
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/165Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
    • G02F1/1675Constructional details
    • G02F1/1676Electrodes
    • G02F1/16761Side-by-side arrangement of working electrodes and counter-electrodes
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/165Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
    • G02F1/1675Constructional details
    • G02F1/1676Electrodes
    • G02F1/16762Electrodes having three or more electrodes per pixel
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/165Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
    • G02F1/1675Constructional details
    • G02F1/1677Structural association of cells with optical devices, e.g. reflectors or illuminating devices
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/165Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
    • G02F1/1675Constructional details
    • G02F2001/1678Constructional details characterised by the composition or particle type
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2203/00Function characteristic
    • G02F2203/11Function characteristic involving infrared radiation

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Molecular Biology (AREA)
  • Geometry (AREA)
  • Mathematical Physics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
  • Special Wing (AREA)
  • Threshing Machine Elements (AREA)
  • Laser Beam Printer (AREA)
  • Glass Compositions (AREA)

Abstract

The invention relates to an infrared reflectivity control device comprising at least one cell (1) which forms a housing comprising a top cover (2) that is transparent in the visible range and a bottom plate (3) bearing at least two electrodes (4a, 4b) which can be connected to an electrical generator (5), the housing enclosing a fluid (6) that is transparent in the visible range and which is charged with particles (7). This device is characterised in that: - the top cover (2) and the fluid (6) are transparent in the wavelength range from 2.5 micrometres to 20 micrometres; - the electrodes (4a, 4b) are reflective in the infrared range; - the electrodes (4a, 4b) are asymmetric, a first electrode (4a) having a first surface area and a second electrode (4b) having a second surface area, the first surface area being greater than the second surface area; - the particles (7) are of nanometric particle size and comprise at least one material capable of being electrically charged (non-zero zeta potential).

Description

Description Title of the invention: Device for controlling the
infrared reflectivity
[00011 The technical field of the invention is that of
devices for controlling the infrared reflectivity of a
support.
[0002] The problem of controlling the infrared
reflectivity of a support arises in many fields.
Temperature control of structures exposed to solar
radiation, e.g. glazing or satellites orbiting the
earth, can be cited. Such reflectivity control is
further encountered in the military field in the design
of camouflages for vehicles, stationary structures or
even persons.
[0003] Patent US2018/0267382 is known in the field of
camouflage, which proposes a structure comprising two
arrays of crossed electrodes arranged on both sides of
cells wherein are housed beads containing a fluid loaded
with particles of various sizes and natures.
[0004] The electrode array allows pixel-by-pixel
addressing and selective cell control. Associated with a
suitable control means, such device can be used for
producing camouflage patterns of various colors and also
an infrared masking by using particles which either
reflect or absorb well near infrared radiation
(wavelength less than 2 micrometers).
[0005] A lower layer of the device blocks infrared
radiation, in particular the radiation coming from the
structure to be masked. The variations in the electric
field between the electrodes make it possible to
distribute the particles so as to obtain the desired
camouflage in the visible or near infrared range.
[0006] Such structure of device is particularly complex
and cannot be used for an effective infrared masking of
a support, in particular in the mid-infrared range
(range generally covering wavelengths from 2.5
micrometers to 20 micrometers). Particles with multiple
masses and electrical properties impair the
effectiveness of masking, particularly in the infrared
range.
[0007] In particular, it is difficult to provide either
absorption of infrared radiation or reflection of said
radiation, because each type of behavior is associated
with particles of a different nature which are mixed in
the same fluid and which have then to be moved in a
differentiated manner.
[0008] U.S. Pat. No. 2008/211764 discloses a display for
controlling the reflectivity, the display using a fluid
which is transparent in the visible range, and is loaded
with particles. Such display uses the phenomenon of
electrophoresis for producing different types of
displays. However, such display is limited to controlling the color of the display between white and
black or between two or a plurality of colors. Such a
display cannot be used for controlling the reflectivity
or the emissivity of a cell in the mid-infrared range,
as defined above. It does not give either any details on
the absorption or transparency properties of the fluid
in said wavelength range.
[0009] U.S. Pat. No. 7034987 discloses an electrophoretic
display which can generate a colored image. The display
comprises a visible volume to which at least one
reservoir for electrophoretic particles is attached. The
reservoir contains at least two types of particles, each
of which is transparent in a first portion of the
optical spectrum and either absorbent or reflecting for a second portion of the spectrum. Such display increases the contrast and brightness of the display, but does not allow to control the infrared reflectivity or emissivity in the mid-infrared range.
[00010] It is the aim of the present invention to propose a simple-design device for controlling infrared reflectivity, providing continuous performance with respect to infrared radiation, ranging from the absorption of radiation to the reflection of radiation.
[00011] The device according to the invention is thus a device with variable emissivity which is more particularly intended for providing a control of the reflectivity in the wavelength range from 2.5 micrometers to 20 micrometers (range corresponding to what is generally called mid-infrared). Said range includes in particular, the bands II and III. Band II: Wavelength from 3 micrometers to 5 micrometers. Band III: Wavelengths from 8 micrometers to 12 micrometers.
[00012] Thus, the device according to the invention is a device for an effective control of the infrared emissivity of the support to which it is applied, which greatly increases the masking potential in the mid infrared range.
[00013] Such performance provides excellent infrared masking whatever the nature of the environment of the structure to be masked.
[00014] It also makes it possible to provide a good control of the temperature of the support, which allows glazing or insulating walls to be produced.
[00015] Thus, the subject matter of the invention is an infrared reflectivity control device comprising at least one cell forming a housing comprising an upper cover transparent in the visible range and a bottom plate bearing at least two electrodes which can be connected to an electric generator, the housing containing a fluid which is transparent in the visible range and is loaded with particles, the device being characterized in that:
- the upper cover (2) and the fluid (6) are transparent
in the wavelength range from 2.5 micrometers to 20
micrometers, corresponding to the mid-infrared;
- the electrodes are reflecting in the infrared range;
- the electrodes are unsymmetrical, a first electrode
having a first surface area and a second electrode
having a second surface area, the first surface area
being greater than the second surface area; - the particles have nanometric particle size and
comprise at least one material which can be electrically
charged (non-zero zeta potential), the particle size
being chosen so as to ensure infrared absorption in the
wavelength range from 2.5 micrometers to 20 micrometers.
[00016] Advantageously, the electrodes can cover at least
90% of the surface area of the bottom plate.
[00017] Advantageously, the first surface area will be much
greater than that of the second surface area, e.g. the
first surface area will be at least ten times greater
than the second surface area.
[00018] According to a particular embodiment, the
electrodes can be transparent in the visible range.
[00019] According to a particular embodiment, the
electrodes can be formed of parallel strips arranged in
an alternating manner, the first electrode including
wide strips and the second electrode including narrow
strips, two consecutive wide strips being separated from
each other by a narrow strip.
[00020] According to a particular embodiment, the strips
can include an alternation of slots and tabs.
[00021] According to a first variant, the slots and tabs
can have rectangular shapes.
[00022] According to a second variant, the slots and tabs can have triangular shapes.
[00023] Advantageously, the material which can be charged can be a metal oxide doped with a metal, such material having a particle size comprised between 40 and 80 nanometers.
[00024] In particular, the material which can be charged can be chosen from the following materials: aluminum doped zinc oxide (Al: ZnO), gallium-doped Zinc Oxide (Ga: ZnO), indium-doped Zinc Oxide (In: ZnO), niobium doped titanium dioxide (Nb: TiO2), tin-doped indium oxide (ITO). ITO is concretely a mixture of indium oxide In203 and tin oxide SnO2.
[00025] Advantageously, the material can be present in the fluid at a concentration of 10 to 60 milligrams per milliliter.
[00026] The invention will be better understood by reading a detailed description made with reference to the appended drawings wherein:
[00027] [Fig. 1] shows schematically an exemplary embodiment of a cell of a reflectivity control device according to the invention;
[00028] [Fig. 2] represents the cell in emissive mode;
[00029] [Fig. 3] represents the cell in reflecting mode;
[00030] [Fig. 4] shows a front view of a first embodiment of the electrodes of the cell;
[00031] [Fig. 5] shows a cell comprising electrodes according to the first exemplary embodiment, and a sectional view along the plane of which line AA is identified in Figure 4;
[00032] [Fig. 6a] shows, in front view, a second exemplary embodiment of the electrodes of the cell;
[00033] [Fig. 6b] shows, in front view, a third exemplary embodiment of the electrodes of the cell;
[00034] [Fig. 7] is a diagram of an infrared reflectivity control device implementing a plurality of cells;
[00035] [Fig. 8] is a diagram showing an infrared reflectivity control device according to the invention associated with masking cells in the visible range.
[00036] Figure 1 shows schematically a cell 1 of an infrared reflectivity control device for a structure, e.g. a vehicle (structure not shown).
[00037] The cell 1 forms a housing 1 comprising an upper cover 2 which is transparent in the visible range and the range of wavelengths from 2.5 micrometers to 20 micrometers (mid-infrared), and a bottom plate 3 which bears at least two electrodes 4a and 4b which can be connected to an electric generator 5. The housing 1 contains a fluid 6 which is transparent in the visible range and the range of wavelengths from 2.5 micrometers to 20 micrometers (mid-infrared), and which is loaded with particles 7. As an example, an isoparaffinic hydrocarbon fluid of the type sold by Exxon Mobil under the brand name Isopar (of type L, M or G) can be used as a fluid. It is also possible to use an alkane, such as: octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, hexadecane, etc.
[00038] The bottom plate 3 will e.g. be a glass plate and the electrodes 4a and 4b will be deposited on said plate by conventional vapor deposition techniques or by screen printing.
[00039] The cover 2 will consist e.g. of a polyethylene film. The only function thereof is to provide leak tightness to the housing 1 containing the fluid 6 loaded with particles 7. Other transparent materials in the visible range and in the range of wavelengths from 2.5 micrometers to 20 micrometers (mid-infrared) would be possible, e.g. parylene or poly (p-xylylene).
[00040] According to a characteristic of the invention, the
electrodes are made of a material reflecting in the
infrared range. The electrodes 4a and 4b can e.g. be
metallic (e.g. chromium deposits on the plate 3).
[00041] According to a particular embodiment, the
electrodes 4a and 4b can be made of a material which is
reflecting in the infrared range and also transparent in
the visible range, e.g. of ITO or of PEDOT-PSS. In a
manner well known to a person skilled in the art, ITO
(or indium tin oxide) is an alloy of indium oxide
(In203) and tin oxide (SnO2).
[00042] PDOT-PSS designates a mixture of two polymers,
poly(3,4-ethylenedioxythiophene) (or PEDOT) and sodium
polystyrene sulfonate (or PSS).
[00043] The choice of transparent electrodes in the visible
range provides the transparency of cell 1, which allows
the overlay thereof with any other effective camouflage
technology in the visible range. A visible camouflage
can be a simple static camouflage canvas or an adaptive
camouflage means, e.g. an electronically controlled
camouflage. Such a variant will be described in detail
thereafter.
[00044] According to another feature of the invention, the
electrodes 4a and 4b are unsymmetrical. Thus, a first
electrode 4a has a first surface area and a second
electrode 4b has a second surface area and the first
surface area is greater than the second surface area.
The difference between the values of each surface area
makes it possible to characterize the extreme positions
the cell can be in, from the point of view of reflection
or absorption. Advantageously, a relatively large
difference can be taken between the values of the two
surface areas, e.g. it is possible to take a first surface area which is at least ten times greater than the second surface area.
[00045] Figure 1 shows schematically, a first electrode 4a positioned in the middle of the bottom plate 3 and a second electrode 4b consisting of two small bars arranged on either side of the first electrode 4a and at a distance therefrom.
[00046] The two bars 4b are electrically connected to each other, either by external connectors as shown, or by etched tracks (not shown) borne by the bottom plate 3.
[00047] According to another feature of the invention, the particles 7 have nanometric particle size and comprise at least one material which can be electrically charged. Such a material which can be charged, is often referred to as having a non-zero zeta potential.
[00048] A nanometric particle size for a powder material is generally less than 100 nanometers. For the particles 7 which are used herein, a particle size comprised between 40 and 80 nanometers will be chosen. Such range corresponds to the optimum providing infrared absorption in the wavelength range from 2.5 micrometers to 20 micrometers (mid-infrared) and in particular in the bands II and III which are the observation ranges of the main infrared detectors.
[00049] The choice of a material with a non-zero zeta potential makes it possible to obtain a stable suspension of the particles 7 in the fluid 6. The choice of a nanometric particle size coupled with the choice of a material with a non-zero zeta potential (conducting) makes it possible to endow the particles of the material with plasmonic properties. The plasmonic effect makes it possible to have a very intense absorption in a well defined wavelength range. The nanometric particle size further prevents the effect of light scattering in the visible range.
[00050] In particular, the plasmonic properties of a granular material have the advantage of increasing the infrared absorption capacity of the material.
[00051] As an example, a metal oxide doped with a metal, e.g. zinc oxide doped with aluminum (Al: ZnO) can be chosen as a material.
[00052] Such material can be easily supplied. The doping of the particles is about 2% of aluminum atoms against 98% of zinc atoms. The crystal lattice of such particles is a Wirtzite structure.
[00053] Preferentially, the material present in the fluid will have a concentration of 10 to 60 milligrams per milliliter.
[00054] Such concentration range makes it possible to obtain a significant modulation of the reflectivity and also makes it possible to obtain a stable suspension.
[00055] Tests made it possible to verify that, in the infrared frequency bands from 3 to 5 micrometers and from 8 to 12 micrometers, infrared absorption was about 70% higher with a concentration of 40 milligrams per milliliter of aluminum-doped zinc oxide compared to a concentration of 10 milligrams per milliliter.
[00056] It should be noted that, in the same infrared bands, the absorption of a fluid loaded with aluminum doped zinc oxide with a concentration of 10 milligrams per milliliter is 25% to 50% greater than the absorption of the fluid alone.
[00057] Such numbers show the significant absorption performance of the granular material which is proposed.
[00058] Figure 2 shows the cell 1 when the generator 5 applies a voltage difference between the two electrodes 4a and 4b. The charge of the first electrode 4a is here greater than the charge of the second electrode 4b. As a result, an electrophoretic displacement of the particles
7 in the fluid 6 (said particles are naturally
negatively charged) takes place. Said displacement
mainly occurs in a lateral direction with respect to the
cell, i.e. parallel to the cover 2 and to the bottom
plate 3.
[00059] Substantially all of the particles 7 are here
concentrated on the first electrode 4a (wide electrode)
and the second electrode 4b is completely clear.
[00060] Thus, the particles 7 mask the first electrode 4a,
the reflecting face of which is covered. As a result,
the cell 1 has an emissive behavior, no longer
reflecting the infrared waves it can receive from the
outside, but absorbing them at the level of particles 7.
[00061] Conversely, in Figure 3, when the generator 5
reverses the voltages between the two electrodes 4a and
4b, all the particles 7 concentrate on the second
electrodes 4b, leaving the first electrode 4a completely
clear. Since the first electrode 4a is reflecting for
infrared waves, the cell 1 is then in a reflecting mode.
It reflects substantially all the infrared waves which
reach it from the outside.
[00062] It should be noted that, for a given cell, the most
reflecting state for the infrared waves (electrode 4a
totally clear) and the most absorbing state for the
infrared waves - so-called emissive state - (electrode
4a totally covered) will depend on the relative surface
areas of the two electrodes. It is thus particularly
advantageous that there is a large difference between
the surface areas of the two electrodes so that the
reflecting or absorbing states of the cell are very
pronounced.
[000631 Concretely, a direct voltage will be applied for
moving the particles from one electrode to another. The
voltage is cut off so as to stop the movement of the
particles. Depending on how long the direct voltage is
applied, a greater or lesser quantity of particles will
group together on the wide electrodes or on the narrow
electrodes. The state of the cell can thus be substantially continuously controlled between the
emissive mode thereof and the reflecting mode thereof.
Advantageously, a low frequency (10 Hz) alternating
voltage is applied for homogeneously dispersing the
particles within the cell. Such dispersion will be
carried out before a new direct voltage is applied in
one direction or the other.
[00064] Advantageously, the electrodes 4a and 4b (and more
particularly the first electrode 4a) cover at least 90%
of the surface area of the bottom plate. The goal is to
give the cell a significant reflecting capacity when it
is in its reflecting state. It is thus necessary that
the greater part of the surface area of the bottom plate
3 is reflecting for infrared waves (due to the first
electrode 4a).
[00065] Figures 1 to 3 are schematic figures showing more
clearly the functioning of the cell according to the
invention.
[00066] Concretely, the electrodes 4a and 4b have a special
shape providing the cell with maximum infrared
reflectivity in the reflecting mode and also a
homogeneous distribution of the particles, a guarantee
of maximum infrared absorption, in the emissive mode.
[00067] Figure 4 shows, in front view, the bottom plate 3
of a cell 1 including a first exemplary embodiment of
the electrodes 4a and 4b. Said figure can be studied in
parallel with Figure 5 which shows the associated cell
1, in a section along the plane of which the line AA is
shown in Figure 4.
[000681 As can be seen in Figure 4, the electrodes 4a and
4b consist of parallel strips which are arranged in an
alternating manner. The first electrode 4a includes wide
strips Bi and the second electrode 4b includes narrow
strips bi, two consecutive wide strips B1 and B2 being
separated from each other by a narrow strip bl.
[00069] All the wide strips Bi are electrically connected
to one another by a first small bar 8a.
[00070] All the narrow strips bi are electrically connected
to one another by a second small bar 8b.
[00071] The first small bar 8a is electrically connected to
a first connection track 9a.
[00072] The second small bar 8b is electrically connected
to a second connection track 9b.
[00073] Thus, when the cell 1 is in the reflecting state,
all the particles 7 are grouped on the narrow strips bi.
The wide strips Bi are then clear and the infrared
reflecting surface area is maximum.
[00074] When, conversely, cell 1 is in the emissive state,
all particles 7 are grouped on the wide strips Bi. The
surface area of the narrow strips bi is much smaller
than the surface area of wide strips Bi and the
absorption of infrared waves by the particles is
maximum.
[00075] Of course, the widths of the wide strips and of the
narrow strips, as well as the width of the spaces
separating these, can be modified. What is important is
to always have at the cell a large difference of surface
area between the wide and narrow strips while covering a
maximum of the surface area of the bottom plate 3.
[00076] It was thus possible to test wide strips, the width
of which varied between 200 micrometers and 500 micrometers, associated with 20 micrometers wide narrow strips.
[00077] The space between the wide strips and narrow strips could be varied between 110 micrometers and 20 micrometers.
[00078] Other shapes are possible for the first electrode 4a and the second electrode 4b.
[00079] Figure 6a thus shows wide strips Bi and narrow strips bi each including an alternation of slots Ci/ci and tabs Li/li. Every tab li of a narrow strip bi is housed in a slot Ci of a wide strip Bi. In parallel, every tab Li of a wide strip Bi is housed in a slot ci of a narrow strip bi.
[00080] In the embodiment shown in Figure 6a, the slots and tabs have rectangular shapes.
[00081] The result of such embodiment is a greater covering of the surface of the bottom plate. Such variant further reduces the accumulation of particles.
[00082] Figure 6b shows another embodiment which is similar to the embodiment shown in Figure 6a, but for which the slots CI/ci and tabs Li/li have triangular shapes.
[00083] Figure 7 shows a device 10 for controlling the infrared reflectivity which uses a plurality of cells 1 assembled on a common support 11, e.g. a fabric or a rigid plate borne by a structure.
[00084] All the cells 1 have a structure of the previously described type. However, every cell 1 can be controlled individually by a control means 12 provided with means enabling same, by addressing, to apply a particular voltage to every cell 1 so as to endow same with a particular emissive or reflecting state.
[00085] Such state will be defined by a calculation means incorporated in the control means 12 and which will be associated e.g. with a camera means enabling it to determine the infrared emission or absorption characteristics of the support surrounding the structure bearing the device. Patent EP2992292 e.g., which describes such a device, can be consulted.
[00086] It thus becomes possible to endow the device 10
with a particular infrared signature which varies from
cell to cell.
[00087] As an example, Figure 7 shows cells la, lb, 1c
having different emissive or reflecting states.
[00088] Figure 8 shows a cell 1, the bottom plate 3 of
which is transparent in the visible range. The bottom
plate is positioned on three cells K1, K2 and K3
containing cholesteric liquid crystals, making it
possible to obtain a coloration which is: blue for K1,
green for K2, and red for K3, respectively. Every cell
K1, K2 and K3 can be controlled individually by a
control means with a more or less intense dosage of each
color.
[00089] Cells for obtaining colors with a more or less
strong intensity level are known, e.g. from patent
EP3213146.
[00090] The stack of cells 1, K1, K2 and K3 is fastened
onto a structure S to be camouflaged.
[00091] Due to the invention, it becomes possible to
combine the masking in the visible range provided by the
cells K1, K2 and K3 with an infrared masking provided by
the cell 1.
[00092] It is of course also possible to associate the
cells 1 with a support, the camouflage pattern of which
is fixed.

Claims (1)

1- An infrared reflectivity control device comprising
at least one cell (1) forming a housing comprising an upper cover (2) transparent in the visible range and a bottom plate
(3) bearing at least two electrodes (4a, 4b) which can be
connected to an electric generator (5), the housing
containing a fluid (6) which is transparent in the visible
range and is loaded with particles (7), characterized in
that:
- the upper cover (2) and the fluid (6) are transparent in
the wavelength range from 2.5 micrometers to 20 micrometers;
- the electrodes (4a, 4b) are reflecting in the infrared
range; - the electrodes (4a, 4b) are unsymmetrical, a first
electrode (4a) having a first surface area and a second
electrode (4b) having a second surface area, the first
surface area being greater than the second surface area; - the particles (7) have nanometric particle size and
comprise at least one material which can be electrically
charged (non-zero zeta potential), the particle size being
chosen so as to provide infrared absorption in the wavelength
range from 2.5 micrometers to 20 micrometers.
2- The infrared reflectivity control device according
to claim 1, characterized in that the electrodes (4a, 4b)
cover at least 90% of the surface area of the bottom plate
(3). 3- The infrared reflectivity control device according
to one of claims 1 or 2, characterized in that the first
surface area is at least ten times greater than the second
surface area
4- The infrared reflectivity control device according
to one of claims 1 to 3, characterized in that the electrodes
(4a, 4b) are transparent in the visible range.
5- The infrared reflectivity control device according to one of claims 1 to 4, characterized in that the electrodes (4a, 4b) are formed from parallel strips (Bi, bi) arranged in an alternating manner, the first electrode (4a) including wide strips (Bi) and the second electrode (4b) including narrow strips (bi), two consecutive wide strips being separated from each other by a narrow strip. 6- The infrared reflectivity control device according to claim 5, characterized in that the strips (Bi, bi) include an alternation of slots and tabs. 7- The infrared reflectivity control device according to claim 6, characterized in that the slots and the tabs have rectangular shapes. 8- The infrared reflectivity control device according to claim 6, characterized in that the slots and the tabs have triangular shapes. 9- The infrared reflectivity control device according to one of claims 1 to 8, characterized in that the material which can be charged is a metal oxide doped with a metal, the material having a particle size comprised between 40 and 80 nanometers. 10- The infrared reflectivity control device according to claim 9, characterized in that the material which can be charged is chosen from the following materials: aluminum doped zinc oxide (Al: ZnO), gallium-doped Zinc Oxide (Ga: ZnO), indium-doped Zinc Oxide (In: ZnO), niobium-doped titanium dioxide (Nb: TiO2), tin-doped indium oxide (ITO). 11- The infrared reflectivity control device according to claim 10, characterized in that the material is present in the fluid (6) at a concentration of 10 to 60 milligrams per milliliter.
AU2021252630A 2020-04-08 2021-03-29 Infrared reflectivity control device Pending AU2021252630A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR2003338 2020-04-08
FR2003338A FR3109219B1 (en) 2020-04-08 2020-04-08 Infrared reflectivity control device
PCT/IB2021/052578 WO2021205280A1 (en) 2020-04-08 2021-03-29 Infrared reflectivity control device

Publications (1)

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AU2021252630A1 true AU2021252630A1 (en) 2022-11-03

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EP (1) EP4133330A1 (en)
AU (1) AU2021252630A1 (en)
FR (1) FR3109219B1 (en)
IL (1) IL297140A (en)
WO (1) WO2021205280A1 (en)

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7956841B2 (en) * 1995-07-20 2011-06-07 E Ink Corporation Stylus-based addressing structures for displays
AU2003202761A1 (en) * 2002-02-19 2003-09-09 Koninklijke Philips Electronics N.V. Electrophoretic display device
WO2008007302A2 (en) * 2006-07-11 2008-01-17 Koninklijke Philips Electronics N.V. Electrophoretic device and method for controlling the same
FR3005350B1 (en) 2013-05-03 2015-04-17 Nexter Systems ADAPTIVE MASKING METHOD AND DEVICE
FR3028052B1 (en) 2014-10-31 2017-12-08 Nexter Systems REFLECTIVE CELL WITH MODULABLE REFLECTIVITY
US10656493B2 (en) * 2014-12-02 2020-05-19 University Of Cincinnati Two particle electrophoretic laminate for use with smart windows
US10642121B2 (en) 2017-03-02 2020-05-05 Korea Electronics Technology Institute Reflective display device for visible light and infrared camouflage and active camouflage device using the same

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IL297140A (en) 2022-12-01
FR3109219B1 (en) 2024-03-29
WO2021205280A1 (en) 2021-10-14
EP4133330A1 (en) 2023-02-15
FR3109219A1 (en) 2021-10-15

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